(1) The Field of the Invention
This invention is generally concerned with the art of providing a road or highway surface with center-lines, or traffic-dividing lines, edge lines or other traffic regulating indicia, generally linear and arranged lengthwise of the road, said lines being formed by applying and firmly securing to the surface of the road pavement a prefabricated sign-forming tape material laid upon a relatively thin underlayer (usually termed "primer layer" in the art) of a generally thermoplastic composition usually comprising bitumen or asphalt or the like, capable of thoroughly filling any road pavement surface hollow, hole or pore, thus providing a tape material receiving impervious, flat and planar surface which achieves a firm and permanent bond of said tape material to the road pavement.
More specifically, this invention is concerned with a method and a machine specially designed for applying and securing to a roadway pavement traffic regulating lines and sign as above by performing the various necessary operations even if the road surface is extremely wet and during rainy or otherwise very unfavourable weather.
(2) The Prior Art
The art of road surface marking by making use of prefabricated tape material, as above, is a well worked one and a wide technical and patent literature exists thereabout. The present applicant has carried out a many years long experimental and actual work and has made many improvements to such art. Such improvements related to tape materials, to primer layer compositions, to methods for forming and applying said primer layers and said tape materials. Many problems concerned with the art might be considered as having heretofore been solved. A number of other problems are however still unsolved, principally concerning the forming of road surface signs and lines over an essentially wet and cold road pavement, and principally when operating during a rainy or otherwise unfavourably weather.
For better acknowledge of the prior art most pertinent of this invention a number of prior U.S. patents of the present applicant will hereinbelow be referred to.
Prefabricated tape materials having antiskid and high nighttime visibility properties, and various improvements thereto, have been described in the U.S. Pat. Nos. 3,587,415, 3,935,365 and 4,020,211, and also in my patent application Ser. No. 617,447, filed on Sept. 26, 1976 (now U.S. Pat. No. 4,069,281).
Machines for forming a suitable primer layer, compositions therefor and devices for laying a prefabricated tape material on said layer; and their improvements, have been described in my prior U.S. Pat. Nos. 3,007,838, 3,155,564, 3,235,436, 3,844,669, and 3,964,559. Some devices adapted to complement said machines have been described in my U.S. Pat. No. 3,964,835.
The principal problems encountered and faced in the most convenient selection of the compositions of the primer layer, and of the various temperature and time parameters involved in forming predominantly thermoplastic primer layers and in securing that the formed sign or indicium will be rapidly able to resist the traffic, have been extensively discussed in my U.S. patent application Ser. No. 652,523 filed on Jan. 26, 1976 (now U.S. Pat. No. 4,082,587).
The present applicant has recently devised and proposed a new and advantageous method for forming a traffic regulating line or indicium on a road pavement, by substantially applying the above considered basic art. Such new method is object of my co-pending patent application Ser. No. 758,693, filed Jan. 12, 1977 and matured into U.S. Pat. No. 4,102,718.
Such new method comprises the sequential steps of melting an at least predominantly thermoplastic primer, firmly bonding the molten primer as a layer to a face of the tape material to thereby form a two-layered indicium band, and pressing said indicium band down against the road surface while the primer layer is in an at least partially molten condition and with sufficient force to drive the primer layer into pores and cavities of the road surface.
In consideration of the fact that a preferred embodiment of this invention, as hereinbelow described, contemplates the use of said improved method, inter alia, the expression "primer and tape two-layered band", or an equivalent one, will be made use of for defining in the following description and in the appended claims, the above indicated composite stratified material designed to be unitarily laid on and secured to the road pavement.